Protective helmet with shock absorbing suspension



March 31, 1959 R. R. HORNICKEL ETAL 3 PROTECTIVE HELMET WITH SHOCK ABSORBING SUSPENSION Filed Nov. 2, 1956 2 Sheets-Sheet 1 1N ENTORS' 6 4097 lVIEAI/cm \lou-flu 1?. Flt/mg ,wn aw Tms'lL me e-vs,

March 31, 1959 R. R. HORNICKEL ETAL 2,879,513

PROTECTIVE HELMET WITH SHOCK ABSORBING SUSPENSION Filed'Nov. 2, 1956 2 Sheets-Sheet 2 nited States Patent PROTECTIVE HELMET WITH SHOCK ABSORBING SUSPENSION Robert R. Hornickel, Pittsburgh, and Joseph R. Fisher, Penn Township, Pa., assignors to Mine Safety Appliances Company, Pittsburgh, Pa., a corporation of Pennsylvania Application November 2, 1956, Serial No. 620,056 Claims. (Cl. 2-3) This invention relates to protective helmets or safety hats, and more particularly to means therein for absorbing the shock of accidental impacts.

The well known protective helmet or hat worn by industrial workers and miners has a rigid shell in which there is a suspension, which includes a cradle of straps that rest on the head with their lower ends connected to the lower part of the shell to support it. The purpose of the suspension is to fit the helmet to the head and space the head from the shell so that downward impacts against the shell will not be transmitted directly to the head. Cradle straps are ordinarily made from a woven webbing that has a high degree of elasticity. These straps transmit force to the wearers head during impact in the following manner; The initial transfer begins at the instant impact and rapidly increases to the point where the webbing ceases to stretch. At this instant the magnitude of the force becomes great if the impact is one of high energy. If the impacting mass is substantially balanced on the shell or has partly penetrated it and is being loosely held by the shell, the energy transfer does not stop when this mass is halted in its downward travel. 0n the contrary, the energy stored in the elastic webbing through its elongation is now released and the impacting mass is accelerated upward. As it is propelled away from the shell, there is a corresponding reacting force on the head. Below its elastic limit the webbing acts as a storer of energy, similar to a spring, and not as an absorber.

It is among the objects of this invention to provide a protective helmet in which the suspension serves as a real shock absorber, and in which the energy absorbing material is formed into separate elements incorporated in the cradle straps of the suspension.

In accordance with this invention a head-receiving cradle for the rigid shell of a protective helmet is formed from a plurality of straps provided with loops. The

upper ends of the straps are connected together, and means are provided for connecting the lower ends of the straps to the shell in order to support it on the head of the wearer. Incorporated in the strap loops is energy "absorbing material, which is adapted to absorb enough energy to fail if the tension on the straps exceeds a predetermined value when the shell receives a downward impact. The energy absorbed by the material in this way reduces the shock of the impact by that amount. The energy absorbing material may be threads which hold the loops in shape, or it may be crushable brittle members holding the loops expanded.

The invention is illustrated in the accompanying drawings, in which Fig. 1 is a bottom view of a helmet looking up into it;

Fig. 2 is an enlarged central longitudinal section;

Fig. 3 is a bottom view of another embodiment;

Fig. 4 is an enlarged longitudinal section of Fig. 3;

Fig. 5 is a fragmentary section of a further modification;

rigid crown 1 which is surrounded by a rigid gig. 6 is a view, like Fig. 5, of a further embodiment; an

Figs. 7 and 8 are views, similar to Fig. 1, of still further modifications of our invention.

Referring to Figs. 1 and 2 of the drawings, the helmet may be made in co'nventinal form of any suitable material, such as metal, fiber glass or laminated plastic, which will provide it-with a shell consisting of a dome-shaped brim 2. The suspension inside the shell includes several flexible cradle straps 3 extending up into the crown from circumferentially spaced points around its lower part. Each strap is doubled upon itself and brought together at its lower end, where it is rigidly connected to the crown by one or more rivets 4 or the like. The rivets also extend through a fairly stifi fiber strip 6 which is sewed to a headband 7 The upper end of each cradle strap is looped around a-strong cord 8, the ends of which are tied together to form a crown lace that connects the upper ends of all of the straps. The straps fit over the head of the wearer and hold the shell in position with its top spaced from the head.

Near the upper end of each cradle strap, its two layers are sewed together very strongly at two points spaced apart lengthwise of the strap to form between them a loop 10 of a predetermined size. Each loop is expanded and filled with energy absorbing material, such as a crushable brittle material preferably in the form of a block-11 which fits snugly enough in the loop to hold itself in place. The block material is hard and strong enough to oiier considerable-resistance to crushing, but it will break or collapse when enough force is applied to it and it will not attempt to return to its original form. For this purpose an expanded brittle material can be used; cellular cellulose. acetate or an expanded thermoplastic vinyl resin being very suitable. Foam glass or a crushable granular material likewise can be used.

During normal use of the helmet the energy absorbing blocks are strong enough to retain their shape and to even sustain blows of moderate force against the helmet. However, when the shell receives a downward impact exceeding a predetermined value considered dangerous to the head, the downward pressure on the shell produces such great tension on the cradle straps that the tendency of the loops to flatten and elongate is great enough to cause the blocks to fail. That is, the blocks are crushed by the pressure of the loops, as shown in broken lines in Fig. 1, and the cradle and helmet shell slide down farther on the head. The energy required to crush the blocks in this manner is absorbed by the cradle and therefore is not transmitted to the head. Consequently, the shock of the impact against the shell is greatly reduced before it can react against the head.

Another way of using this same principle is illustrated in Figs. 3 and 4, wherein the loops 15 are located at the upper or inner ends of the cradle straps 16 Where they are doubled on themselves. Laced through these loops is the cord 17 that forms the crown lace which connects the straps together. A crushable block of the same kind of energy absorbing material described above is disposed in each loop betweenthe lace and the inner end of the loop. In other "words, thelace surrounds all of the blocks. To help hold the'la'ce in that position, each block maybe provided with a groove 18 that receives the lace. When excessive force is exerted downward against the helmet shell 19, the tendency of the cradle straps to pull outward away'from one another causes the blocks to be crushed by the loops and against the confining lace as shownin broken lines in Fig. 4. The ,energy absorbed in' crushing the blocks reduces the shock of the impact against the head.

In Fig. 5, a further modification is shown which does not use crushable energy absorbing material. Instead, each cradle strap has a portion folded back and forth to form a loop 21, which is held in shape by a thread 22 stitched across the strap. The thread is made of any suitable material, but must be strong enough to avoid breaking when the helmet shell 23-receives blows below a predetermined value. On the other hand, if the force of a blow exceeds that value, the threads will be broken by the tendency of the straps to straighten out the loops, as shown in broken lines. The energy consumed in breaking the threads is absorbed or lost and is not transmitted to the head of the wearer.

The advantage of the modification shown in Fig. 6 is that the energy absorbing material does not depress the cradle strapsbelow their normal position, thereby avoiding possible uncomfortable pressure points. This is accomplished by not fastening the superimposed layers of each cradle strap 25 together anywhere except at their upper and lower ends, the upper ends being integrally connected. A crown lacing cord 26 connects the upper ends of the straps in the usual way. The two layers of each strap are held apart near their upper ends, so that a loop is formed, by means of a block 27 of crushable energy absorbing material. To permit one layer of the strap to be free to position itself relative to the other layer, the block is fastened to only one layer, preferably the lower one. This may be done in various ways, such as by a flexible sleeve or bag 28 containing the block and sewed or otherwise fastened to the strap. When severe tension is exerted on the straps, their upper layers will be pulled down tightly against the blocks in the loops and the blocks will be crushed.

In the embodiment illustrated by Fig. 7, freely adjustable strap loops are again used, but the crushable blocks 30 are mounted in flexible pockets 31 formed in the loops on one of the strap layers. It is therefore preferred to mold the straps 32 of a suitable plastic so that the pockets can be integral with them and formed at the same time. If desired, part of the side wall of each pocket can be provided with a flexible extension that forms a cover 33 for the pocket to help hold the block in place. Also, the straps may even be molded integrally with the headband 34.

The embodiment of Fig. 8 utilizes two different straps, a long one 36 and a short one 37, to form each strap loop. Here again it is preferred to make them from a molded plastic. The lower ends of the long straps are connected with a headband 38, but their upper ends 39 extend up through transverse slots 40 in the upper end portions of the short straps. The upper ends of the long straps are thickened and enlarged transversely so that they will not pull out of the slots. Yet, by proper manipulation they can be removed and inserted in a like slot at a different level to help adjust the cradle vertically. The short straps are part of a crown piece 41, which rests on top of the head and from which the straps radiate. The short straps extend part way down the long straps in overlapping relation with them, and their enlarged lower ends 42 extend through selected slots 43 in the long straps to connect them. Disposed in the loop between each pair of overlapping straps is a pocket 44 joined to one of them and containing a crushable, energy absorbing block.

It will be understood that with any of the cradles disclosed herein it may not always be necessary to use the blocks with all of the straps. Also, the stitched loop shown in Fig. -5 could be combined with a crushable block in the same strap if desired. Furthermore, there may be cases ,where it is desirable to have different blocks crush under different loads, so that they will not all fail at the same time.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However,'I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. In the rigid shell of a protective helmet, a headreceiving cradle comprising a plurality of straps provided with expanded loops, means for connecting the lower ends of the straps to the shell to support it on a head, and separate crushable brittle members surrounded by said loops, said members being adapted to be crushed by the pressure of said loops if the tension on the straps exceeds a predetermined value when the shell receives a downward impact, whereby the shock of said impact will be reduced.

2. In the rigid shell of a protective helmet, a headreceiving cradle comprising a plurality of straps provided with expanded loops, means for connecting the lower ends of the straps to the shell to support it on a head, and a crushable block of brittle material in each loop and holding it expanded, said blocks being adapted to be crushed by the flattening of the loops if the tension on the straps exceeds a predetermined value when the shell receives a downward impact, whereby the shock of said impact will be reduced.

3. In the rigid shell of a protective helmet, a headreceiving cradle comprising a plurality of straps provided at their upper ends with expanded loops, a cord extending through the loops to connect the upper ends of the straps, means for connecting the lower ends of the straps to the shell to support it on a head, and separate crushable brittle members surrounded by said loops between said cord and the inner ends of the loops, said members being adapted to be crushed against said cord by the pressure of said loops if the tension on the straps exceeds a predetermined value when the shell receives a downward impact, whereby the shock of said impact will be reduced.

4. In the rigid shell of a protective helmet, a headreceiving cradle comprising a plurality of straps provided at their upper ends with expanded loops, a cord extending through the loops to connect the upper ends of the straps, means for connecting the lower ends of the straps to the shell to support it on a head, and a separate crushable block of brittle material mounted in each loop and surrounded thereby between said cord and the inner end of the loop, the block being provided with a central groove receiving the cord, said blocks being adapted to be crushed by the pressure of said loops against them if the tension on the straps exceeds a predetermined value.

5. In the rigid shell of a protective helmet, a headreceiving cradle comprising'a plurality of straps, each strap being doubled upon itself to form superimposed layers having their free ends adjacent the bottom of the shell, a cord extending between the layers of each strap at their upper ends to connect the upper ends of the straps, means for connecting said free ends to the shell to support it on a head, each pair of said superimposed layers being connected only at their opposite ends, a crushable brittle member disposed between the superimposed layers of each of a plurality of the straps, and means for fastening said brittle material to only one layer of each strap, said members being adapted to be crushed by the pressure of the adjoining superimposed strap layers against them if the tension on the straps exceeds a predetermined value when the shell receives a downward impact, whereby the shock of said impact will be reduced.

6.A head-receiving cradle according to claim 5, in which said fastening means includes a flexible container for the crushable member, and means for attaching the container to a strap layer.

7. A head-receiving cradle according to claim 5, in

which said fastening means includes a flexible pocket joined with a strap layer and containing the crushable member.

8. In the rigid shell of a protective helmet, a head receiving cradle comprising a plurality of long straps, means for connecting the lower ends of the straps to the shell to support it on a head, a flexible crown piece provided with radiating short straps overlying the upper portions of said long straps, the lower ends of the short straps being secured to the long straps, the upper ends of the long straps being secured to the upper ends of the short straps to form expanded loops between the superimposed portions of the straps, and separable crushable brittle members in surrounded by said loops, said members being adapted to be crushed by the pressure of said loops if the tension on the straps exceeds a prede- 1 References Cited in the file of this patent UNITED STATES PATENTS Gross Aug. 14, 1956 Fisher et a1. June 25, 1957 

